Forrageamento em Achaearanea cinnabarina levi 1963 (Araneae, Theridiidae) e evolução da caça em aranhas de teia irregular

Abstract

Orbweb monophyly and its evolution towards monophyletic irregular webs are a recent demonstration of the utility of behaviour on phylogenetic analyses. The loss of web regularity implies a change in prey signal reception by the spider, and therefore should be accompanied by changes in the hunting repertoire. We investigate this hypothesis by comparing hunting tactics in Achaearanea cinnabarina Levi 1963 with that of other theridiids and also with orbweavers. We have videotaped 40 captures of two prey taxa; the sessions have been transcribed with the program Observer Video Pro and afterwards analyzed with the program EthoSeq. Achaearanea cinnabarina hunting routines are extremely plastic, so that they probably will show a low level of taxonomic information. Nevertheless there is also a large number of context independent routines, routines which occur with both prey types, and these routines are probably useful for cladistic analysis. Achaearanea cinnabarina unconditionally uses the wrap-bite strategy, one that is used mainly towards dangerous prey among orbweavers. This is probably a result of evolutionary changes in the diet (ants are a major prey of theridiids), which in turn are probably the result of combined changes in web structure and website selection. Thus, the evolution of orbwebs to theridiid cobwebs resulted in a reduction of the hunting repertoire.